In U.S. Pat. No. 4,530,268, Starrett describes a stringed musical instrument that embodies a matrix of intersecting frets and strings. Strings and frets are mounted in an intersecting relationship on a generally rectangular fingerboard. The strings are tuned by string tensioning means, including tuning pins or pegs. The string vibrations are sensed by a magnetic pickup and the resulting signal is amplified by an amplifier. The strings and frets each define a number of notes, equal to at least the number of notes of an octave. The instrument is played by depressing a string into contact with a fret. This action is called ‘fretting’ the strings. In a first scheme of modulation, multiple strings may be played along a single fret in a manner similar to a piano. In a second scheme of modulation, different frets are played to obtain different notes, as in a guitar, to achieve a wide tonal range with easy fingering positions. Vertically adjustable magnetic pickups sense the vibrations and are able to change the vibration sensitivity of the instrument.
At least thirteen strings are used to represent an octave, each string being separated by a semitone from the next adjacent string. Similarly, the frets intersecting a given string ascend in semitones for an octave. The strings are passed across a bridge and are secured to the fingerboard by appropriate tensioning means. Adjustment of the string tension is used to provide various temperaments.
One disadvantage of the Starrett instrument is that to play an octave interval using the first modulation scheme requires that thirteen strings be spanned. Starrett discloses an octave span that is the same distance as an octave span on a piano. Anthropometrical analysis will reveal that intervals much larger than this would be a difficult stretch from thumb to little finger of the same hand. It would therefore be difficult to play intervals much larger than an octave with one hand. In particular, it would be difficult to play ‘open-voiced’ chords that span large overall intervals (such as the greater-than two-octave chords playable on a guitar) with one hand. Moreover, among all possible equal-temperament tuning systems, Starrett's semitone tuning system requires the largest number of strings when matching the complete note range of another instrument such as guitar or piano. More strings result in higher cost, a larger and heavier instrument, and longer tuning time.
A still further disadvantage is that the instrument is heavy and difficult to carry, since it has a larger number of strings and a larger body compared to other stringed instruments (such as electric guitar).
A still further disadvantage is that notes cannot be sustained after finger removal (using a sustain pedal for example), since the fret selection is lost when a finger is removed from a string.
A still further disadvantage is that when a finger is lifted from a string, open strings may be plucked or sounded unintentionally.
A still further disadvantage is that strings used for the highest notes must be of smaller cross-sectional diameter than those for the lowest notes and consequentially produce weaker vibration signals. While Starrett's variable-distance magnetic pickups help to compensate for this, by bringing certain magnets within closer proximity to their respective strings, such compensation is limited by the adverse effects of increased magnetic pull on the strings (loss of sustain, for example).
A further disadvantage is that the use of magnetic pickups requires the use of metal strings, which can be uncomfortable to play. Additionally, magnetic pickups are commercially packaged in groups of four or six with predetermined spacing that is dissimilar from Starrett's spacing and not adjustable.